Realization of low-loss high-reflection mirrors is desired to increase the performance of interferometry and laser gyro and to realize quantum computers based on cavity quantum electrodynamics.
As a mirror, there is known a configuration of stacking a plurality of pairs of a high refractive index layer and a low refractive index layer. Non-Patent Document 1 proposes a configuration of stacking a plurality of layers having a continuously changed refractive index to suppress loss due to scattering at the interface between the high refractive index layer and the low refractive index layer.
In this configuration, the electric field is nearly zero in the portion where the refractive index discontinuously increases. In the entire region except the boundary where the refractive index is discontinuous, the refractive index continuously changes, and the refractive index difference is small. Hence, it is considered that the interface scattering loss is suppressed as compared with the configuration of stacking a plurality of pairs of a high refractive index layer and a low refractive index layer. However, in this configuration, the reflectance is likely to decrease. Thus, it is difficult to realize low loss and high reflection at the same time.